Benzoxocarbocyanines and method of preparation



May 11, 1948. A. w. ANISH 2,441,342

' BENZOXOCARBOCYANINES AND METHOD OF PREPARATION Filed March 10, 1944 J2a6 40 44 4a 52 $0" 50 [xampZe I ATTORN EY Patented May 11, 1948 UNITEDSTATE S PATENT ()FFICE BENZOXOCARBOCYANINES AND METHOD OF PREPARATIONAlfred W. Anish, Johnson City, N. Y., assignor to General Aniline & FilmCorporation, New York, N. Y., a corporation of Delaware ApplicationMarch 10, 1944, Serial No. 525,935

1 Claim.

My invention relates to new benzoxocarbocypreparation of'such dyes, theinvention relates to new 2-alkylbenzoxazoles containing as a substituentin the aryl nucleus isomeric (secondary and tertiary) alkyl oraryl-alkyl groups.

The preparation of symmetrical benzox'ocarbocyanines is well known inthe prior art. I have found, however, that the introduction of the abovementioned alkyl or aryl-alkyl groups in the benzene nucleus of suchcarb-ocyanines have an unusual and novel efi'ect in sensitizingphotographic emulsions, which effect is highly desirable. I havediscovered that the presence of these groups in the benzoxocarbocyaninesproduces a steep or sharp cut-off in the spectral curve as shown in theaccompanying drawing. Such characteristics are highly desirable,especially in sensitizing dyes used in color photography emulsions,where it is desired that the multi-layer emulsions be sensitive tocertain wave lengths.

My novel dyes may be represented by the follovn'ng structural formula:

In the above formula R represents an isomeric (secondary and tertiary)alkyl or aryl-alkyl group, such as isobutyl, cumyl, isoamyl, tertiaryamyl, tertiary hexyl, isopropyl, diisobutyl, 2-, or 3-methylbutylgroups, The groups which represent R may be the same or different in thedye.

B may be substituted in any suitable position in the benzene nucleus ofthe dyes, such as,'for example the 5, 5', 6 or 6' position.

R1 and R2 represent an alkyl, aryl or aralkyl group such as methyl,ethyl, c ethoxyethyl, butyl, allyl or benzyl.

X represents any anion such as, for example, Cl, Br, I, C104, NOa,SO4CH3, SO4C2'H5,

, 2 or any other acid radical forming an alkyl or aralkyl ester. 7

The novel intermediates from which the above dyes may be prepared can berepresented by the following structural formula:

C-Rs

In the above formula R has the same significanoe as this symbol in theformula for the dyes given above. R3 stands for analkyl group.

It is accordingly an object of my invention to provide newbenzoxocarbocyanine dyes and new intermediates'for preparing the same. Afurther object is to provide a process for preparing such new products.Other objects will become apparent from the description which follows:

In accordance with my invention, I prepare the novel dyes by condensinga Z-methylbenzoxazole quaternary ammonium salt which is substituted inthe benzene nucleus by a secondary or tertiary alkyl or aryl-alkylgroup, in the presence of a suitable condensing agent, as for exampleethyl o-iormate. The intermediates are prepared from z nitro-phenolswhich are substituted in the benzone nucleus by a secondary or tertiaryalkyl or aryl-alkyl radical. Such nitro-phenols may be preparedaccording'to the process of U. S. Patent No. 2,207,727. Thenitro-compound is then reduced to form the corresponding phenol amine,and the latter is finally reacted with a fatty acid, fatty acidanhydride or fatty acid-fatty acid anhydridemixture, such as aceticacid, acetic acid anhydride or a, mixture of the two, to form thesecondary or tertiary substituted 2-alkylbenzoxazole.

'The following examples will serve to illustrate the method of formingthe new benzoxocarbocyanine dyes:

Example 1.-1.l diethyl-6.6'-dicumyl benzoxocarbocyanine iodide for 3hours. The reaction mix was then cooled and poured into water containing'pota'ssiumio- 3 4 dide and allowed to stand. The dye crystals were Asillustrative of the new 2-alkylbenzoxazole filtered and washed withwater, and finally reintermediates and their method of preparation,crystallized from ethyl alcohol. Brilliant yelthe following examples aregiven: low, flat, prism-shaped dye crystals were obtained. The dye meltsat 270 C. and yields a 5 Example 4 p am W Sharp Cut-01T as Shown in2-nitro-4-tertiary-butyl-pheno1 was prepared Fleure by the'methoddescribed in U. s. 2.207.727 as porated in a gelat o s er emulfollows:150 grams of p-tertiary-butyl-phenol in 81011 Containing about 45% ofsilver iodide, the 500 cc. of benzol was nitrated with a mixture of dyeimparts to it a range of SenSitiVeIleSS from 128.0 cc. of 70% nitricacid and 256.0 cc. of water. o t 360 u to about 569 i Withwsharp maXi'Thenitro, compound was vacuum distilled and mum at a ou 540 M- has: aboiling point of 136 C. at 1% mm. The Example y ynitro-tertiary-butyl-phenol was then reduced o o a b cya d d withalkaline'sodium hydrosulfite as follows:

0 O grams of 2-nitro-4-tertiary-butyl-phenol in 800 cc. of 10% causticsoda solution were C OH=OH CH=C. (3H3 heftfgsted.h3g2:1 C. $111101 751:0gralnlgslof SOGIZJI? hydrosu e.a e. eceara aine souion was F acidifiedwith dilute acetic acid and the white H3 l C i 20 crystalline plates of2-amino-4-tertiary-butyl- 02135 I phenolprecipitated. The compound meltsat 2.4 gms. each of Z-methyl-B-tertiary-butyl- 162-4c C. The yieldobtained was 16.4 grams. benzoxazole-ethyl-p-toluene sulfonate and ethyly atmg 44.7 grams of the dried amino-tertio-formate were condensed byrefluxing in 10.0 cc. arY-b Y -D W a l a t c ac d, or with of pyridinefor hours. T cooled reaction anacetic acid-acetic acid anhydride mixturemixture was poured into. water containing three Containing 75 6 f egrams of 2-met yl grams of potassium iodide. and allowed to stand. -t fiY- yle zoxazole were obtained. The The water was decanted, the residuewas washed compound has a B. P. of 137 C. at 16 mm. with water followedby ethyl ether and then crys- When heated with ethy p-toluene sulfonate,tallized twice from ethanol. Red rhombic crysthe substituted benzoxazoleis converted into the tale were obtained. The dye melts at 257 C.orrespondin q aternary ammonium salt.

and yields a spectrogram having a sharp cut-off as shown in'Fig. 2.Example 5 Incorporated'in a gelatino silver bromide emul-2-nitroi-cumylphenol was prepared by nision containing about 45% ofsilver iodide, the trating a mixture of 24.2 grams of p-cumyldye impartsto it aran'ge of sensitivenessfrom phenol in 40.0 cc. of benzol with amixture of about 360 m to about 560 my. with a sharp maxi- 1218 cc. of70% nitric acid in 25.6 cc. of water at mum at about 535 mu. 7-10 C. Thenitro compound has a boiling point Example 3.-1.1"diethyl-6.6-diisoamy1-benzof 145 C. at 15 mm. 2-amin0-4-cumyl-phenoloxocarbocyanine perchlorate; 40 was obtained from the nitro compound byal- A mixture'o'f 20 guns. of 2-methyl-6-isoamylkaline sodiumhydrosulfite reduction. 2-methylb'enzoxazole-ethy1-p-toluene sulfonateand 2.0 fi-cumy-l-benzoxazole was then prepared by regms. of ethylo-formate in 10.0 cc. ofpyridine was fluxing 8.2 grams of the2-amino-4-cumyl-pheheated for 2% hours; The cooled reaction mixn01 withan acetic acid-acetic anhydride mixture wasv diluted with water and onstanding ture containing 15 cc. of each, and finally dry separated as anoil. After repeated washings distilling the reaction mixture. TheZ-methyl-fiwith water the oil was dissolved in alcohol andcumyl-benzoxazole obtained boils at 162 C. at diluted with a 10%sodium-perchlorate solution. 16 mm.

The dye crystals were separated and recrystal- When heated with ethylp-toluene sulfonate, lized from ethyl alcohol. Red, blue reflex thesubstituted benzoxazole is converted into the (rhombic) crystals areobtained. The dye melts corresponding quaternary ammonium salt.

at 25 C. and yields a spectrogram having a Example 6 sharp cut-off asshown in Figure 3.

Incorporated. in a gelatino silver bromide emuli r Y -ph Was prepared bynision containing about 45%' of silver iodide, the trating a mixture ofgrams of D- Y dye imparts to it a range of sensitiveness from phenol in150.0 cc. of benzene with a mixture about 360 m, to about 560 mp with asharp maxici;22-.6.-cc. of nitric acid diluted with 22.6 cc. mum atabout 535 my. of Water at 0-8 G. The nitro compound has a To obtain dyeswith the secondary and tertiary boiling point 145-150 C. at 16 mm. alkylor aryl-alkyl substituent in.the.5i-position, 10.0. grams of theZ-nitro-d-isoarnyl-phenol I start with the corresponding benzoxazole.The thus obtained were reduced with alkaline sodium procedure.is-otherwise the same for making-such 70 hydrosulfite. 16 grams of theamino-compound dyes as in Examples 1, 2 and 3 except that I start soobtained were" dry distilled from an acetic with the benzoxazcle inwhich'the cumyl, tertiacid-acetic anhydride mixture containing 25 cc.ary-butyl and diisoamyl radicles are substituted of each to formZ-methyl-G-isoamyl-benzoxazole. in: the 5-position of the'benzoxazoleinstead of The compound has a B.-P.-of 270 C. at 760 mm.

the 6'-position; and 147 C.at-16 mm.

When heated with ethyl p-toluene sulfonate, the substituted benzoxazoleis converted into the corresponding quaternary ammonium salt.

To form the 5-substituted secondary and tertiary alkyl and aryl-alkylbenzoxazole intermediates I proceed in the same manner as set forth inExamples 4, 5 and 6, except that I start with a Z-nitro-phenol which issubstituted. in the 5-position with a tertiary-butyl, cumyl, or isoamylradical, or any other secondary or tertiary alkyl or aryl-alkyl radical.

The benzoxazoles obtained according to these examples may be convertedto other quaternary ammonium salts by heating with other suitablealkylating agents as ethyl iodide, methyl sulphate ethyl para-toluenesulfonate, diethyl sulphate, ethyl perchlorate, ethyl nitrate or anyalkyl or alkaryl ester.

In general the benzoxazoles and their salts may be prepared according tothe methods set forth in my U. S. Patent 2,429,178, issued October 14,1947.

While the above examples disclose the preparation of the symmetricalcarbocyanine dyes, it is obvious that the unsymmetrical dyes may besimilarly formed. Thus 2-methyl 6 cumylbenzoxazole-ethyl-p-toluenesulfonate may be condensed with2-methyl-G-tertiary-butyl-benzoxazole-ethyl-p-toluene sulfonate in thepresence of ethyl-o-formate to form a dye having the followingstructure.

Czls I Ca s In similar manner, various unsymmetrical dyes may be made byreacting 2-methylbenzoxazoles having different secondary and tertiarysubstituents in the benzene nucleus.

Instead of condensing the benzoxazoles with ortho-for'mic acid esters,formaldehyde may be used. Likewise, the 2-p-acetanilidovinyl derivativesof the secondary and tertiary substituted benzoxazoles may be condensedwith the secondary and tertiary substituted 2-alkylbenzoxazoles, suchas, for example, the 2-methyl benzoxazoles to form the newbenzoxocarbocyarfines. The Z-p-acetanilidovinyl derivatives may beprepared according to the method set forth in my U. S. Patent 2,429,179,issued October 14, 1947.

The benzoxazole may be condensed with thiazoles or heterocycliccompounds other than benzoxazoles. But I have found that the resultingunsymmetrical dyes no longer have a sharp cut-off, but flat maxima.

6 The dye may be substituted in the central carbon atom of thepolymethine chain by an alkyl or other group. However, I have found thatthe resulting dye does not have the sharp 5 spectral cut-off in thespectral curve as the dye which is unsubstituted in the polymethinechain.

From the above examples it is apparent that a large number ofcondensations are possible with the novel benzoxazole intermediates. There sulting dyes which are formed are highly useful as sensitizers forphotographic silver halide emulsions, giving a sharp cut-off in thespectral curve.

The accompanying drawing illustrates and depicts the sensitivity ofemulsions containing three of my dyes. Each figure is a diagrammaticreproduction of a spectrogram showing the sensi-- tivity of a silverbromide emulsion containing one of my dyes.

Fig. 1 shows the sensitivity of an ordinary gelatino-silver bromideincluding silver iodide and containing the dye of Example 1. It depictsthe steep cut-off in the spectral curve.

Fig. 2 shows the sensitivity of an ordinary gelatino-silver bromideincluding silver iodide and containing the dye of Example 2. It depictsthe steep cut-off in the spectral curve.

Fig. 3 shows the sensitivity of an ordinary gelatino-silver-bromideincluding silver iodide and containing the dye of Example 3. It depictsthe steep cut-off in the spectral curve.

I claim:

1.1'-diethyl-6.6'-dicumyl-benzoxocarbocyanine iodide characterized bythe following formula:

\COH=OHOH=O H506? |-CuH N N HaC CHI C2/H5 \I (52H; ALFRED W. ANISH.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,060,383 Schneider Nov. 10, 19362,066,967 Dieterle Jan. 5, 1937 2,173,486 Schneider Sept. 19, 19392,230,257 Middleton Feb. 4, 1941 2,233,599 Brooker Mar. 4, 19412,354,524 Kumetal July 25, 1944 OTHER REFERENCES Ser. No. 419,570,Reister (A. P. 0.), pub. Apr. 20, 1943.

